1. Field of the Invention
The present invention relates to a thermosensitive recording material, and more particularly to a thermosensitive recording material which forms a colored image as a result of a chemical coloring reaction of an electron donating coloring agent with an electron accepting coloring developer.
2. Discussion of the Related Art
A thermosensitive recording material is well known in which a colored image is formed by a chemical coloring reaction of a colorless or a pale colored coloring agent, such as an electron donor, e.g., a leuco dye having a lactone, a lactam or a spiropyran ring, with a coloring developer, such as an electron acceptor, e.g., an organic acid or a phenolic compound, wherein color formation is induced when the coloring agent and the coloring developer are subjected to heat or the like.
The thermosensitive recording material has the following advantages over other conventional recording media:
(1) color images can rapidly be recorded by a relatively simple apparatus without using such complicated steps as developing and fixing; PA1 (2) color images can be recorded without producing noise and environmental pollution; PA1 (3) various color images, e.g., red, blue, violet and black, can easily be obtained; PA1 (4) image density and background whiteness are high; and PA1 (5) the manufacturing cost is low. PA1 (1) sticking occurs in which the surface of the recording layer sticks to the thermal printhead because of the good contact of the recording layer and the thermal printhead, thereby deteriorating image qualities or feeding properties of the thermosensitive recording materials; PA1 (2) the thermal printhead easily wears out when an inorganic filler is added to the recording layer in order to decrease the sticking; and PA1 (3)a part or a component of the recording layer is melted or softened and toughly adhered to the thermal printhead due to the heat applied for recording images, resulting in occurrence of undesired white streaks in the recorded images because the part of the thermal printhead to which the extraneous substance is adhered has insufficient heat conduction. PA1 (1) adding a wax to the protective layer; PA1 (2) employing a silicone modified resin as a resin of the protective layer, if desired, together with other resin; PA1 (3) adjusting the mixing ratio of the resin to the total amount of the organic fillers; and/or PA1 (4) changing the composition of the organic fillers. PA1 (1) dispersing each organic filler in a solvent or a resin solution using, for example, a ball mill to prepare organic filler dispersing liquids; PA1 (2) mixing the organic filler dispersing liquids, if desired, together with an additional resin solution to prepare a protective layer coating liquid; PA1 (3) coating the protective layer coating liquid on a recording layer using a conventionally known coating method; and PA1 (4) drying the coated liquid to form a protective layer. PA1 2-anilino-3-methyl-6-diethylaminofluoran, PA1 2-anilino-3-methyl-6-(di-n-butylamino)fluoran, PA1 2-anilino-3-methyl-6-(N-n-propyl-N-methylamino)fluoran, PA1 2-anilino-3-methyl-6-(N-isopropyl-N-methylamino)fluoran, PA1 2-anilino-3-methyl-6-(N-isobutyl-N-methylamino)fluoran, PA1 2-anilino-3-methyl-6-(N-n-amyl-N-methylamino)fluoran, PA1 2-anilino-3-methyl-6-(N-sec-butyl-N-ethylamino)fluoran, PA1 2-anilino-3-methyl-6-(N-n-amyl-N-ethylamino)fluoran, PA1 2-anilino-3-methyl-6-(N-n-isoamyl-N-ethylamino)fluoran, PA1 2-anilino-3-methyl-6-(N-n-propyl-N-isopropylamino)- fluoran, PA1 2-anilino-3-methyl-6-(N-cyclohexyl-N-methylamino)-fluoran, PA1 2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluoran, PA1 2-anilino-3-methyl-6-(N-methyl-p-toluidino)fluoran, PA1 2-(m-trichloromethylanilino)-3-methyl-6-diethylamino-fluoran, PA1 2-(m-trifluoromethylanilino)-3-methyl-6-diethylamino-fluoran, PA1 2-(m-trifluoromethylanilino)-3-methyl-6-(N-cyclohexyl-N-methylamino)fluoran PA1 2-(2, 4-dimethylanilino)-3-methyl-6-diethylaminofluoran, PA1 2-(N-ethyl-p-toluidino)-3-methyl-6-(N-ethylanilino)-fluoran, PA1 2-(N-methyl-p-toluidino)-3-methyl-6-(N-propyl-p-toluidino)fluoran, PA1 2-anilino-6-(N-n-hexyl-N-ethylamino)fluoran, PA1 2-(o-chloroanilino)-6-diethylaminofluoran, PA1 2-(o-bromoanilino)-6-diethylaminofluoran, PA1 2-(o-chloroanilino)-6-dibutylaminofluoran, PA1 2-(o-fluoroanilino)-6-dibutylaminofluoran, PA1 2-(m-trifluoromethylanilino)-6-diethylaminofluoran, PA1 2-(p-acetylanilino)-6-(N-n-amyl-N-n-butylamino)fluoran, PA1 2-benzylamino-6-(N-ethyl-p-toluidino)fluoran, PA1 2-benzylamino-6-(N-methyl-2, 4-dimethylanilino)fluoran, PA1 2-benzylamino-6-(N-ethyl-2, 4-dimethylanilino)fluoran, PA1 2-benzylamino-6-(N-methyl-p-toluidino)fluoran, PA1 2-benzylamino-6-(N-ethyl-p-toluidino)fluoran, PA1 2-(di-p-methylbenzylamino)-6-(N-ethyl-p-toluidino)-fluoran, PA1 2-(.alpha.-phenylethylamino)-6-(N-ethyl-p-toluidino)fluoran, PA1 2-methylamino-6-(N-methylanilino)fluoran, PA1 2-methylamino-6-(N-ethylanilino)fluoran, PA1 2-methylamino-6-(N-propylanilino)fluoran, PA1 2-ethylamino-6-(N-methyl-p-toluidino)fluoran, PA1 2-methylamino-6-(N-methyl-2, 4-dimethylanilino)fluoran, PA1 2-ethylamino-6-(N-methyl-2, 4-dimethylanilino)fluoran, PA1 2-dimethylamino-6-(N-methylanilino)fluoran, PA1 2-dimethylamino-6-(N-ethylanilino)fluoran, PA1 2-diethylamino-6-(N-methyl-p-toluidino)fluoran, PA1 2-diethylamino-6-(N-ethyl-p-toluidino)fluoran, PA1 2-dipropylamino-6-(N-methylanilino)fluoran, PA1 2-dipropylamino-6-(N-ethylanilino)fluoran, PA1 2-amino-6-(N-methylanilino)fluoran, PA1 2-amino-6-(N-ethylanilino)fluoran, PA1 2-amino-6-(N-propylanilino)fluoran, PA1 2-amino-6-(N-methyl-p-toluidino)fluoran, PA1 2-amino-6-(N-ethyl-p-toluidino)fluoran, PA1 2-amino-6-(N-propyl-p-toluidino)fluoran, PA1 2-amino-6-(N-methyl-p-ethylanilino)fluoran, PA1 2-amino-6-(N-ethyl-p-ethylanilino)fluoran, PA1 2-amino-6-(N-propyl-p-ethylanilino)fluoran, PA1 2-amino-6-(N-methyl-2, 4-dimethylanilino)fluoran, PA1 2-amino-6-(N-ethyl-2, 4-dimethylanilino)fluoran, PA1 2-amino-6-(N-propyl-2, 4-dimethylanilino)fluoran, PA1 2-amino-6-(N-methyl-p-chloroanilino)fluoran, PA1 2-amino-6-(N-ethyl-p-chloroanilino)fluoran, PA1 2-amino-6-(N-propyl-p-chloroanilino)fluoran, PA1 2, 3-dimethyl-6-dimethylaminofluoran, PA1 3-methyl-6-(N-ethyl-p-toluidino)fluoran, PA1 2-chloro-6-diethylaminofluoran, PA1 2-bromo-6-diethylaminofluoran, PA1 2-chloro-6-dipropylaminofluoran, PA1 3-chloro-6-cyclohexylaminofluoran, PA1 3-bromo-6-cyclohexylaminofluoran, PA1 2-chloro-6-(N-ethyl-N-isoamylamino)fluoran, PA1 2-chloro-3-methyl-6-diethylaminofluoran, PA1 2-anilino-3-chloro-6-diethylaminofluoran, PA1 2-(o-chloroanilino)-3-chloro-6-cyclohexylaminofluoran, PA1 2-(m-trifluoromethylanilino)-3-chloro-6-diethylamino-fluoran, PA1 2-(2, 3-dichloroanilino)-3-chloro-6-diethylaminofluoran, PA1 1, 2-benzo-6-diethylaminofluoran, PA1 1, 2-benzo-6-(N-ethyl-N-isoamylamino)fluoran, PA1 1, 2-benzo-6-dibutylaminofluoran, PA1 1, 2-benzo-6-(N-ethyl-N-cyclohexylamino)fluoran, and PA1 1, 2-benzo-6-(N-ethyl-p-toluidino)fluoran, PA1 dodecyl phosphonate, PA1 tetradecyl phosphonate, PA1 hexadecyl phosphonate, PA1 octadecyl phosphonate, PA1 eicosyl phosphonate, PA1 docosyl phosphonate, PA1 tetracosyl phosphonate, PA1 hexacosyl phosphonate, and PA1 octacosyl phosphonate. PA1 .alpha.-hydroxydodecyl phosphonate, PA1 .alpha.-hydroxytetradecyl phosphonate, PA1 .alpha.-hydroxyhexadecyl phosphonate, PA1 .alpha.-hydroxyoctadecyl phosphonate, PA1 .alpha.-hydroxyeicosyl phosphonate, PA1 .alpha.-hydroxydocosyl phosphonate, and PA1 .alpha.-hydroxytetracosyl phosphonate. PA1 dihexadecyl phosphate, PA1 dioctadecyl phosphate, PA1 dieicosyl phosphate, PA1 didocosyl phosphate, PA1 monohexadecyl phosphate, PA1 monooctadecyl phosphate, PA1 monoeicosyl phosphate, PA1 monodocosyl phosphate, PA1 methyl hexadecyl phosphate, PA1 methyl octadecyl phosphate, PA1 methyl eicosyl phosphate, PA1 methyl docosyl phosphate, PA1 amyl hexadecyl phosphate, PA1 octyl hexadecyl phosphate, and PA1 lauryl hexadecyl phosphate. PA1 .alpha.-hydroxydecanoic acid, PA1 .alpha.-hydroxytetradecanoic acid, PA1 .alpha.-hydroxyhexadecanoic acid, PA1 .alpha.-hydroxyoctadecanoic acid, PA1 .alpha.-hydroxypentadecanoic acid, PA1 .alpha.-hydroxyeicosanoic acid, PA1 .alpha.-hydroxydocosanoic acid, PA1 .alpha.-hydroxytetracosanoic acid, PA1 .alpha.-hydroxyhexacosanoic acid, and PA1 .alpha.-hydroxyoctacosanoic acid. PA1 2-bromohexadecanoic acid, PA1 2-bromoheptadecanoic acid, PA1 2-bromooctadecanoic acid, PA1 2-bromoeicosanoic acid, PA1 2-bromodocosanoic acid, PA1 2-bromotetracosanoic acid, PA1 3-bromooctadecanoic acid, PA1 3-bromoeicosanoic acid, PA1 2, 3-dibromooctadecanoic acid, PA1 2-fluorododecanoic acid, PA1 2-fluorotetradecanoic acid, PA1 2-fluorohexadecanoic acid, PA1 2-fluorooctadecanoic acid, PA1 2-fluoroeicosanoic acid, PA1 2-fluorodocosanoic acid, PA1 2-iodohexadecanoic acid, PA1 2-iodooctadecanoic acid, PA1 3-iodohexadecanoic acid, PA1 3-iodooctadecanoic acid, and PA1 perfluorooctadecanoic acid. PA1 2-oxododecanoic acid, PA1 2-oxotetradecanoic acid, PA1 2-oxohexadecanoic acid, PA1 2-oxooctadecanoic acid, PA1 2-oxoeicosanoic acid, PA1 2-oxotetracosanoic acid, PA1 3-oxododecanoic acid, PA1 3-oxotetradecanoic acid, PA1 3-oxohexadecanoic acid, PA1 3-oxooctadecanoic acid, PA1 3-oxoeicosanoic acid, PA1 3-oxotetracosanoic acid, PA1 4-oxohexadecanoic acid, PA1 4-oxooctadecanoic acid, and PA1 4-oxodocosanoic acid. PA1 dodecylmalic acid, PA1 tetradecylmalic acid, PA1 hexadecylmalic acid, PA1 octadecylmalic acid, PA1 eicosylmalic acid, PA1 docosylmalic acid, PA1 tetracosylmalic acid, PA1 dodecylthiomalic acid, PA1 tetradecylthiomalic acid, PA1 hexadecylthiomalic acid, PA1 octadecylthiomalic acid, PA1 eicosylthiomalic acid, PA1 docosylthiomalic acid, PA1 tetracosylthiomalic acid, PA1 dodecyldithiomalic acid, PA1 tetradecyldithiomalic acid, PA1 eicosyldithiomalic acid, PA1 docosyldithiomalic acid, and PA1 tetracosyldithiomalic acid. PA1 dodecylbutanedioic acid, PA1 tridecylbutanedioic acid, PA1 tetradecylbutanedioic acid, PA1 pentadecylbutanedioic acid, PA1 octadecylbutanedioic acid, PA1 eicosylbutanedioic acid, PA1 docosylbutanedioic acid, PA1 2, 3-dihexadecylbutanedioic acid, PA1 2, 3-dioctadecylbutanedioic acid, PA1 2-methyl-3-dodecylbutanedioic acid, PA1 2-methyl-3-tetradecylbutanedioic acid, PA1 2-methyl-3-hexadecylbutanedioic acid, PA1 2-ethyl-3-dodecylbutanedioic acid, PA1 2-propyl-3-dodecylbutanedioic acid, PA1 2-octyl-3-hexadecylbutanedioic acid, and PA1 2-tetradecyl-3-octadecylbutanedioic acid. PA1 dodecylmalonic acid, PA1 tetradecylmalonic acid, PA1 hexadecylmalonic acid, PA1 octadecylmalonic acid, PA1 eicosylmalonic acid, PA1 docosylmalonic acid, PA1 tetracosylmalonic acid, PA1 didodecylmalonic acid, PA1 ditetradecylmalonic acid, PA1 dihexadecylmalonic acid, PA1 dioctadecylmalonic acid, PA1 dieicosylmalonic acid, PA1 didocosylmalonic acid, PA1 methyloctadecylmalonic acid, PA1 methyldocosylmalonic acid, PA1 methyltetracosylmalonic acid, PA1 ethyloctadecylmalonic acid, PA1 ethyleicosylmalonic acid, PA1 ethyldocosylmalonic acid, and PA1 ethyltetracosylmalonic acid. PA1 2-dodecyl-pentanedioic acid, PA1 2-hexadecyl-pentanedioic acid, PA1 2-octadecyl-pentanedioic acid, PA1 2-eicosyl-pentanedioic acid, PA1 2-docosyl-pentanedioic acid, PA1 2-dodecyl-hexanedioic acid, PA1 2-pentadecyl-hexanedioic acid, PA1 2-octadecyl-hexanedioic acid, PA1 2-eicosyl-hexanedioic acid, and PA1 2-docosyl-hexanedioic acid. PA1 o-palmitylcitric acid ##STR9## o-stearylcitric acid ##STR10## o-eicosylcitric acid ##STR11## PA1 p-(dodecylthio)phenol, PA1 p-(tetradecylthio)phenol, PA1 P-(hexadecylthio)phenol, PA1 P-(octadecylthio)phenol, PA1 p-(eicosylthio)phenol, PA1 p-(docosylthio)phenol, PA1 p-(tetracosylthio)phenol, PA1 p-(dodecyloxy)phenol, PA1 p-(tetradecyloxy)phenol, PA1 p-(hexadecyloxy)phenol, PA1 p-(octadecyloxy)phenol, PA1 p-(eicosyloxy)phenol, PA1 p-(docosyloxy)phenol, PA1 p-(tetracosyloxy)phenol, PA1 p-dodecylcarbamoylphenol, PA1 p-tetradecylcarbamoylphenol, PA1 p-hexadecylcarbamoylphenol, PA1 p-octadecylcarbamoylphenol, PA1 p-eicosylcarbamoylphenol, PA1 p-docosylcarbamoylphenol, PA1 p-tetracosylcarbamoylphenol, PA1 hexadecyl gallate, PA1 octadecyl gallate, PA1 eicosyl gallate, PA1 docosyl gallate, and PA1 tetracosyl gallate. PA1 caffeic acid n-pentyl ester, PA1 caffeic acid n-hexyl ester, and PA1 caffeic acid n-octyl ester. PA1 Sn salt of decylmercaptoacetic acid, PA1 Sn salt of dodecylmercaptoacetic acid, PA1 Sn salt of tetradecylmercaptoacetic acid, PA1 Sn salt of hexadecylmercaptoacetic acid, PA1 Sn salt of octadecylmercaptoacetic acid, PA1 Mg salt of decylmercaptoacetic acid, PA1 Mg salt of dodecylmercaptoacetic acid, PA1 Mg salt of tetradecylmercaptoacetic acid, PA1 Mg salt of hexadecylmercaptoacetic acid, PA1 Mg salt of octadecylmercaptoacetic acid, PA1 Zn salt of decylmercaptoacetic acid, PA1 Zn salt of dodecylmercaptoacetic acid, PA1 Zn salt of tetradecylmercaptoacetic acid, PA1 Zn salt of hexadecylmercaptoacetic acid, PA1 Zn salt of octadecylmercaptoacetic acid, PA1 Cu salt of decylmercaptoacetic acid, PA1 Cu salt of dodecylmercaptoacetic acid, PA1 Cu salt of tetradecylmercaptoacetic acid, PA1 Cu salt of hexadecylmercaptoacetic acid, and PA1 Cu salt of octadecylmercaptoacetic acid. PA1 (1) using a coloring agent and a coloring developer, at least one of which does not dissolve or hardly dissolves in the solvent used for the protective layer coating liquid; PA1 (2) microencapsulating at least one of a coloring agent and a coloring developer to prevent the coloring agent from contacting the coloring developer; and/or PA1 (3) forming a resin layer between a recording layer and a protective layer to prevent the recording layer from contacting a protective layer coating liquid. PA1 (1) dispersing or dissolving a coloring agent, a coloring developer and a binder resin in water and/or an organic solvent to prepare a recording layer coating liquid; PA1 (2) coating the recording layer coating liquid on a substrate by a conventionally known coating method; and PA1 (3) drying the coated liquid to form a recording layer. PA1 polyester films such as polyethyleneterephthalate and polybutyleneterephthalate, PA1 cellulose films such as cellulose triacetate, PA1 polyolefin films such as polyethylene and polypropylene, PA1 polystyrene films, PA1 paper, and PA1 synthetic paper.
Because of these advantages, the above-described thermosensitive recording material can be widely used, not only as a recording material for price labels in stores, but also as recording materials for copiers, printers for computers, facsimiles, automatic vending machines of labels and tickets, video printers and measuring instruments.
These thermosensitive recording materials generally include a thermosensitive recording layer (hereinafter referred to as recording layer) which is formed on a paper substrate and includes a coloring agent and a coloring developer. Recently, since the thermosensitive recording material is required to have good image qualities such as high resolution, the surface of the thermosensitive recording material tends to be enhanced in smoothness, for example, by forming an undercoat layer between a substrate and a recording layer. In addition, as the uses of the thermosensitive recording material grow, it is required to be used for document sheets for over head projection (OHP) or print output sheets for video printers. These thermosensitive recording materials are required to have a plastic film substrate and a smooth recording layer in order to produce an image having good image qualities.
When such a smooth recording layer including materials used for conventional recording layers is formed on a smooth surface of a plastic film substrate, the recording layer exhibits good image density because the contact between the recording layer and a thermal printhead is fairly good; however, the following problems tend to occur:
In attempting to solve these problems, i.e., sticking and white streaks, thermosensitive recording materials having a protective layer which includes a filler and which is formed on the surface of the recording material are disclosed. For example, Japanese Laid-Open Patent Application No. 61-225095 discloses a thermosensitive recording material having a protective layer including an inorganic filler. As mentioned above, this thermosensitive recording material has the drawback that it easily wears out a thermal printhead. Japanese Laid-Open Patent Applications No. 58-025988 and 05-278334 disclose thermosensitive recording materials having a protective layer including an organic filler. These thermosensitive recording materials do not easily wear out a thermal printhead; however, they cannot prevent the occurrence of the sticking and the white streaks.
Because of these reasons, a need exists for a thermosensitive recording material having good image qualities without white streaks and good ability to be used with thermal printheads without shortening the life of the thermal printheads, i.e., without sticking to and wearing out the thermal printheads.